1. Field of the Invention
The present invention relates to a process for producing an electrophotographic photosensitive member.
2. Description of the Related Art
An electrophotographic photosensitive member containing an organic photoconductive substance (hereinafter referred to as “charge generating substance”) is known as an electrophotographic photosensitive member to be mounted on an electrophotographic apparatus. At present, the above-mentioned electrophotographic photosensitive member has been a mainstream electrophotographic photosensitive member to be used in a process cartridge of an electrophotographic apparatus or in the electrophotographic apparatus, and has been put into large-scale production. Of such electrophotographic photosensitive members, a laminated electrophotographic photosensitive member improved in characteristics by separating functions needed for an electrophotographic photosensitive member into its respective layers has been frequently used. A construction obtained by laminating an undercoat layer, a charge generating layer, and a hole transporting layer in the stated order on a support has been adopted as a main construction of the laminated electrophotographic photosensitive member.
A method involving dissolving a functional material in an organic solvent to prepare an application solution (application liquid) and applying the solution onto the support has been generally employed as a method of producing the laminated electrophotographic photosensitive member. The reduction of the organic solvent in the step of forming a coat for each layer has been desired in recent years. Such a proposal as described below has been made in a layer in which a metal oxide has been dispersed or a layer in which an electron transporting substance has been dispersed as a proposal for the reduction of the organic solvent for the undercoat layer of the laminated electrophotographic photosensitive member.
Japanese Patent Application Laid-Open No. 2010-113005 proposes a method involving: forming a coat of a dispersion liquid obtained by dissolving a polyol-based resin and a blocked isocyanate compound in an aqueous dispersion medium, and dispersing metal oxide particles in the medium; and heating the coat to form an undercoat layer in which the metal oxide particles have been dispersed. Japanese Patent Application Laid-Open No. 2012-128397 proposes a method involving: producing a water dispersion liquid containing polyolefin resin particles and particles each containing an electron transporting substance; forming a coat of the dispersion liquid on a support; and forming an undercoat layer by heating the coat to melt the polyolefin resin particles. In Japanese Patent Application Laid-Open No. 2012-128397, the undercoat layer in which the particles each containing the electron transporting substance have been dispersed is formed.
Although the undercoat layer can be formed by using the aqueous dispersion medium in each of the methods disclosed in Japanese Patent Application Laid-Open No. 2010-113005 and Japanese Patent Application Laid-Open No. 2012-128397, an additional improvement in uniformity of the undercoat layer has been required for an additional improvement in image uniformity. In Japanese Patent Application Laid-Open No. 2010-113005, the metal oxide particles each functioning as an electron transporting substance need to be dispersed in an additionally uniform manner. However, it may be difficult to improve dispersibility of the metal oxide particles in the aqueous dispersion medium. In addition, the method disclosed in Japanese Patent Application Laid-Open No. 2012-128397 is a method of forming an undercoat layer in which the electron transporting substance has been dispersed in a state of particles each containing the electron transporting substance, and hence uniformity of a surface of the undercoat layer is liable to reduce. Therefore, a production method by which the organic solvent is reduced and the uniformity of the surface of the undercoat layer is improved upon formation of the undercoat layer has been desired.